Contact lens



April 2, 1940- w FEINBLOOM 2,196,066

CONTACT LENS .Filed March 2, 1938 2 Sheets-Sheet 1 FIG! RADIUS OF'ro'Rus |234s67e9o|| W WILLIAM rz l v gtfigg F G. 7 BY I ATTORNEYSRADIUS 0F GENERATING CIRCLE o a 4 m m b u N m v APril 2, 1940. w.FEINBLOOM 2,196,066

CONTACT LENS Filed March 2, 1938 2 Sheets-Sheet 2 FIG. 8 I lag WILLIAMFEINBL OOM INVENTOR. 29 I BY 1 m, w -azf 2g ATTORNEYS Patented Apr. 2,1940 UNITED STATES PATENT OFFICE.

2 Claims.

The present invention relates to contact lenses. Heretofore, commercialcontact lenses have been of two general types, the ground lenses and theblown lenses. Both of these types are made entirely of glass. The groundcontact lenses were made with both the corneal and scleral portionsspherical and were fitted from test series in which the radii of thescleral rims of the different lenses varied by predetermined steps. Inthe vast majority of cases, these ground lenses are unsatisfactorybecause only a small number of eyes are spherical in the scleral areaand placing a spherical contact glass on a non-spherical eye causeslocal irritation so that the glass cannot be tolerated.

The second general type of commercial contact lens is the blown lens.These lenses are blown against a model of the eyewhich is built upempirically by a trial and error method. The con tact glasses of thistype are thus expensive and diflicult to produce. A further difficultyof these blownlenses is that the optical properties of the cornealsection cannot be accurately controlled and any attempt at subsequentgrinding adds grave technical difliculties and greatly increases theexpense.

Two other forms are also known but neither has had any commercialapplication. 'One of these forms is a contact lens molded entirely fromCellon or Celluloid and due to the optical disadvantages as well as themanufacturing difi'iculties and excessive mold costs, this form hasnever come into commercial use. The other noncommercial form consists ofa glass or Celluloid l5 corneal section mounted in a flexible scleralrim of Celluloid or rubber. For various reasons this lens has never comeinto commercial use. First of all, neither Celluloid nor rubber willstand up well in the eye. Then, too, mere flexibility will 0 not permitthe scleral rim to stretch to fit eyes of different size. Furthermore,the degree of flexibility is dependent on many factors and, where thetolerances are assmall as they are in the eye, a comfortable lens wouldbe difiicult, if 5 not impossible, to reproduce.

Another method of fitting contact lenses is disclosed and claimed in mycopending application Serial No. 72,970 filed April 6, 1936, for Contactlenses which has matured into Patent No.

, 2,129,304 of Sept. 6, 1938. According to this lat ter method, a moldis made from an impression of the eye and a contact lens having amoldable scleral rim is formed by means of this moldj. While veryaccurate and comfortable contact lenses can be produced by this method,the fact that each lens is an individual job throughout, makes themethod somewhat troublesome to practice.

I have found, however, that a very large percentage of eyes can becomfortably fitted with 5 contact lenses from a test series in which thescleral rims are made in toric form rather than the spherical form ofthe ground type of contact lens.

This present application is a continuation in 10 part of my copendingcase Serial No. 72,970 filed April 6, 1936' for Contact lenses.

An object ofthe present invention is to provide a test series of toriccontact lenses. A-further object is to provide a new and improved conl5tact lens. 'A still further object is to provide a corrected contactlens. These and other objects and advantages reside in certain novelfeatures of construction, arrangement and combination of parts andprocesses as will hereinafter be 20 more fully set forth and pointed outin the appended claims.

Referring to the drawings:

Fig. 1 is a rear view of a contact lens or bowl embodying the presentinvention. 25

Fig. 2 is a central section thereof, showing the lens in position on theeye. Fig. 3 shows a portion of the chart for the test series.

Figs. 4, 5 and 6 are rear views of contact lenses 30 modified to changethe area of contact on the eye.

Fig. 7 is a section taken on line 1, 1 of Fig. 4. Fig. 8 is a front viewof a decentered contact lens.

ished to such a curve that, together with the layer of saline solutionI2 between it and the eye I3, it will provide the desired correction forthe eye l3.

The scleral rim H is adapted to rest on the sclera of the eye ii! tohold the lens ill in position before the cornea. As pointed out in myabove-mentioned copending application Serial No. 72,970 filed April 6,1936, this scleral rim H is independent and distinct from the corneallens I0, is separately formed and thelens I0 and rim II can therefore beformed to unrelated curves. 5

Fig. 9 is a vertical section of the lens of Fig. 8. 5 I

.These resins are The scleral rim H is preferably molded or pressed toits desired form and it can be composed of a wide variety of materials.These materials must conform to the following conditions: there must beno surface deterioration or sensible change in shape-when exposed to ahalf normal saline solution at one hundred degrees Fahrenheit; theremust be no injurious products given off when the material is boiled in ahalf normal saline solution; the material must be molded at reasonabletemperatures and pressures; the material must be rigid in thin (one-halfmillimeter) sections; and the material must be capable of taking a highpolish.

A large number of substances can be readily selected to fulfill theseconditions. For example, a large number of synthetic resins are usable.The polyvinyl resin sold under the trade name Vydon, the pyroxylin resinsold under thetrade name Hecolite, the cellulose acetate resin soldunder the trade name Superez, the polystyrene resin sold under the tradename Tepperite, and the polyacrylic acid resin sold under the trade nameKallodent, could be used in this way. of the general type known asthermoplastic and, while they canbe used, they are not the mostdesirable materials because of the temperature and pressure needed forproper molding. Urea resins such as those sold under the trade names ofPlaskon and Beetle, are satisfactory from a molding standpoint but intheir present form, the urea odor makes them undesirable.

I prefer to use a thermosetting resin of the phenol formaldehyde type.One resin of this type which has been tried and found satisfactory, isthe resin sold by the Bakelite Corporation under the identificationnumber Kit-10247. This resin has all of the desired properties and itsease of molding makes it preferable.

From experience, I have found that there are five main factors affectingof contact lenses. These are:

The overall size of the lens. This size is preferably an angular measureand, in'Flgs. 9

' and 10, would be twice the angle a measured from the center of thetorus.

2. The position of the corneal section with respect to the scleral rim.This position is also preferably determined. by an angular measure andis indicated by the angle 13 in Fig. 10.

3. The amount the rear surface of the corneal section is spaced from thecontacting surface of the scleral rim. This distance is preferablymeasured from the edge 26 of the rear surface of the corneal lenssection II to the point directly below on the continued curve of thecontacting surface 29 of the scleral rim 2!. This distance is designatedas S in Fig. 11.

4. The radius of curvature of the scleral part of the lens in thevertical meridian. That is, R1 in Fig. 9.

5. The radius of curvature of the scleral part of the lens in thehorizontal meridian. That is, Rs in Fig. 10.

Other factors, such as the radius of curvature of the inner surface ofthe corneal section and the smallest diameter of the contacting surfaceof the scleral rim, also affect the fit but the five outlined above arethe principal ones.

Of course, a test series could be made in which each of the abovefactors is varied independently but the large number of necessary lensesmakes such a series a practical impossibility. I have found that byselecting values for the first three the fitting qualities I variables,overall size, corneal lens position and corneal lens spacing, and byvarying the horizontal and vertical radii of the scleral rim inpredetermined steps throughout the series, a test series can be madewhich is significantly more effective than any method of fitting knownto the prior art. In other words, such a series will satisfactorily fita much higher percentage of patients than any other known method offitting.

The values selected for the first three variables are not necessarilythe same throughout the series, but each combination of radii of thescleral rim has its own particular size, corneal lens position andcorneal lens spacing. The particular values selected are to bedetermined by experiment. For example, a small eye having a radius ofcurvature of 12 mm. may, in the majority of cases, require a contactlens of a smaller overall size than a large eye having a radius ofcurvature of 15 mm. Likewise, it may be found that in one or morecombinations of radii, a corneal lens centered in the scleral rim ismore satisfactory while in other cases, the majority of patients requirecontact lenses in which the corneal section is decentered in the scleralrim. The corneas of some sizes of eyesmay usually run higher than thoseof other eyes and in such an event, the contact lenses in these sizeswould be made with a greater corneal spacing.

After fitting a large number of patients satisfactorily, I have foundcertain values of the first three variables to be satisfactory in aconsiderable percentage of cases. The angle a can be fixed at a valuebetween 55 and 65". Usually it is preferable to have this angle as largeas possible since by distributing the pressure over a larger area, thecontact lens is less apt to cause irritation. The angle 5 can be fixedat a value between 8 and 12. It would be preferable for manufacturingreasons to fix the angle 3 at zero to form a centered lens as in Fig. 1but I have found such a large proportion of patients requiringdecentered lenses, that I prefer to use decentered lenses throughout theseries. The spacing S can be fixed at a value between 0.25 mm. and 0.75mm. for a large proportion of cases.

The values given in the preceding paragraph are by no means restrictiveand are given merely by way of example. Knowing the factors to be variedin predetermined steps and knowing the ones to be fixed by experiment,anyone skilled in the art can prepare an adequate test set.

Fig. 3 shows a chart designating the radii of the rims of lenses of atest series made in accordance with this invention. The lenses of thistest series are made in toric form and on the chart H, the verticalcolumns designate the radius of the torus R1 while the horizontal rowsdesighate the radius of the generating circle R2. The numbers in the rowII and column 16 are the numerical values'of the radii and the figuresin the row I! and column I! are merely empirical designations of thesenumerical values. Thus the lens represented by the square I! could bedesignated as an 8 x 3 lens more conveniently than as a 13.75 by 12.50spindle toric lens.

The lenses designated by the chart II are made to both the spindle toricform and the ring toric form. The lenses above and to the right of theline 20 being spindle toruses and those below and to the left of theline 2| being ring toruses: The contact lenses designated by the squaresbetween lines 20 and 2| are spheres.

Both the test and finished lenses will preferably u used on either eyeand the have a rim of uniformsize so that they can be axis will beindicated on the finished lens. Of course, it is not necessary toprovide the entire series of both spindle and ring toruses and the testset could comprise toruses of only one type. However, since these twotypes of torus are-quite different in the quadrants, it may be that aspindle torus would fit a particular eye comfortably while the ring tomswould not.

i Thelchart I4 gives only the curves of the scleral r ms same for theentire test series, that is, they will have the same power and the samedimensions.

In fitting contact lenses or bowls from this set, the refractiohist bytrial selects the contact bowl whose scleral rim II properly fits theeye. With this test lens in place, the eye is refracted to determine theproper power'ior the corneal lens I0. The eye is also preferablyexamined with a slit lamp or the like to determine the proper clearancebetween the lens I 0 and the cornea of the eye, as set forth in myapplication Serial No. 37,577 filed June 26, 1936, for Method of andmeans for making contact lenses, which has matured into Patent No.2,178,873 of Nov. 7, 1939'. A lens I0 having the proper power is thensecured in a rim II so that there will be the proper clearance betweenthe lens Ill and the cornea. A suitable method for making this contactlens is disclosed in my above-mentioned application Serial N0. 72,970filed April 6, 1936.

After a proper and comfortable fit is obtained by means of the testseries, it is essential that the prescription contact lens be 'nearly aspossible an exact duplicate of the contact lens of the test series.Referring to Figs. 8, 9, l0 and 11, a con struction is shown in whichthe contact lens is made to exact'reproducible dimensions. figures, thecorneal lens III is decentered in a molded plastic rim 25. The angles aand 5 determining the overall decentration can be readily determined.

Fig. 11 shows in enlarged section the structure of the joint between thelens I0 and the rim 2!. 0n the interior of the contact lens, the plasticrim 25 is ground away on a cone from the point where the edge 28 of thebevel 2'! joins the plastic. This conical surface is designated at 28. Acone is then ground on the rim-25 joining the surface 28 and thecontacting surface 29 of the rim. This 90 conical surface is designatedat 30. The surfaces 28, 29 and 30 are then polished into a smoothsurface substantially as indicated at M.

0n the outer surface of the contact lens a 60 conical surface-32 isformed from the point where the edge 33 of the bevel 21 joins theplastic rim 2!. A flat surface 34 is then formed joining the conicalsurface 32 and the outer surface II of the scleral rim 25. The surfaces32, 34 and 38 are then polished down to form the smooth surface .36. Theoutside of the joint is constructed in this way to prevent the formationof a so-called "feather edge" which might warp away from the bevel 21 ofthe lens ll and irritate the eyelids.

' method of construction.

Preferably, the lenses III will be the.

4 am able to attain the objects of In these size and the amount of Theconstructional details recited in the preceding paragraphs are not,to betaken as restrictive but are given merely as indicating one It isobvious that these details such as angles, locations and distances canbe varied through relatively wide limits within the scope of thisdisclosure.

It may be that a test lens conforms in general shape to the eye buteither fits too tightly or cuts down the flow of lachrymal or otherfluids of the eye. In such a case it is necessary to reduce the area ofcontact between the scleral rim I I and 'the eye 83 in the manner setforth generally in 1938. As shown in Figs. 4 to 7, I prefer to form'grooves or depressions in the scleral rim I I and these can be formedeither by locally modifying the mold used to make the scleral rim II orby grinding out parts of the finished rim.

In the form shown in Fig. 4," the rim II is formed with a series ofgrooves 22 which extend radially to points adjacent the edge of the rimII. The rim II of the lens. shown in Fig. 5 has a plurality of staggeredcircular depressions 23 while the rim II shown in Fig. 6 is providedwith a plurality of random grooves and depressions 24. Only the areabetween these grooves or depressions comes into contact with the eye anda comparison of Fig. 1 with Figs. 4, 5 and 6 shows how the area ofcontact is reduced.

From the foregoing it will be apparent that I my invention and provide anew and improved contact lens. While I have stated that the phenolformaldehyde resin is preferred for the scleral rim of my new contactlens, the requirements of the lens are set forth and other resins orsimilar substances can be used with equivalent results. Variousmodiflcations of my invention can, of course, be made without departingfrom the spirit of my invention or the scope of the appended claims.

I claim:

1. A test series of contact lenses each compriscorneal lenses being ofsubstantially the same size, power and curvature throughout the seriesand located in substantially the same relative positions in-the scleralrims, the scleral rims being of substantially the same size throughoutthe series and having their radii of curvature varied in substantiallyuniform increments independently in the vertical and horizontalmeridians.

2. A test series of contact lenses each having a corneal lens and atoric scleral rim, each corneal lens in the series having substantiallythe same size, curvature and power and being located in substantiallythe same relative podtion in a scleral rim and with substantially thesame build up, the scleral rims in the series being of substantially thesame size, the radii of the-toric rims in the two meridians beinsvariedindements throughout the series.

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